1. Field of the Described Embodiments
The described embodiments relate generally to automobile engine control. More particularly, methods and devices for directing selected engine operations through a diagnostic port during normal operation of an engine using are described.
2. Description of the Related Art
In automobile industry, there is a large aftermarket for devices that affect the factory performance of automobiles. One class of aftermarket devices is geared toward affecting the engine performance. For instance, an aftermarket engine control device can be designed to boost the power of the engine under certain conditions. As another example, an aftermarket device can be configured to cause the engine to burn fuel more efficiently under certain conditions to increase fuel efficiency.
Modern automobile engines include engine control units. The engine control unit determines the amount of fuel, ignition timing and other parameters that affect the performance of an internal combustion engine. Aftermarket devices exist that can be used to overwrite the factory software and/or data in an engine control unit to change the engine performance. For instance, the factory look-up tables and/or control algorithms in the engine control unit that are used to generate the control commands for the engine can be overwritten. The overwrite modification of the engine control unit is performed while the automobile is in a non-operational state, i.e., not being driven, and then, after it is completed, the automobile can be operated, i.e., driven around, using the modified engine control unit.
The factory settings for an engine control unit are selected with the objectives of operating the engine under the conditions that don't needlessly damage the engine and achieving a desired operational lifetime for the engine. The selected factory settings are verified via large amounts of testing. A disadvantage of modifying the factory look-up tables and/or control algorithms in an engine control unit is that it typically voids the warranty the manufacturer provides on the engine. The manufacturer voids the warranty because they don't know whether aftermarket modifications will damage and/or shorten the lifetime of the engine. The possibility of engine damage and reduced engine lifetime are also a concern to a user modifying an engine control unit via an aftermarket device. In view of the above, methods and apparatus are desired that allow the factory engine performance of an automobile to be modified, such as to improve fuel efficiency, that minimize the risks associated with modifying the engine control unit.